In my prior U.S. Pat. No. 4,110,742, an alarm circuit is disclosed for use in combination with industrial machinery. The example given is the coal mining industry where coal tipples employ elongated conveyor belts and the starting controls are in a location where the operator cannot see the entire belt from the control position. The system disclosed in that patent is one which prevents the startup of machinery of that type unless an alarm circuit has first been actuated to sound an alarm for a predetermined period of time to alert all personnel in the area of the machinery that it is about to start. The alarm is so arranged that if the machinery does not start within a predetermined time following termination of the alarm, the entire cycle must be restarted.